New Japanese translation. Forward port from 1.3.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

  <head>

    <meta name="generator" content="HTML Tidy, see www.w3.org" />

    <title>Apache suEXEC Support</title>

  </head>

  <!-- Background white, links blue (unvisited), navy (visited), red (active) -->

  <body bgcolor="#FFFFFF" text="#000000" link="#0000FF"

  vlink="#000080" alink="#FF0000">

    <!--#include virtual="header.html" -->

    <h1 align="CENTER">Apache suEXEC Support</h1>

    <ol>

      <li><big><strong>CONTENTS</strong></big></li>

      <li><a href="#what">What is suEXEC?</a></li>

      <li><a href="#before">Before we begin.</a></li>

      <li><a href="#model">suEXEC Security Model.</a></li>

      <li><a href="#install">Configuring &amp; Installing

      suEXEC</a></li>

      <li><a href="#enable">Enabling &amp; Disabling

      suEXEC</a></li>

      <li><a href="#usage">Using suEXEC</a></li>

      <li><a href="#debug">Debugging suEXEC</a></li>

      <li><a href="#jabberwock">Beware the Jabberwock: Warnings

      &amp; Examples</a></li>

    </ol>

    <br />

     <br />

    <h3><a id="what" name="what">What is suEXEC?</a></h3>

    <p align="LEFT">The <strong>suEXEC</strong> feature --

    introduced in Apache 1.2 -- provides Apache users the ability

    to run <strong>CGI</strong> and <strong>SSI</strong> programs

    under user IDs different from the user ID of the calling

    web-server. Normally, when a CGI or SSI program executes, it

    runs as the same user who is running the web server.</p>

    <p align="LEFT">Used properly, this feature can reduce

    considerably the security risks involved with allowing users to

    develop and run private CGI or SSI programs. However, if suEXEC

    is improperly configured, it can cause any number of problems

    and possibly create new holes in your computer's security. If

    you aren't familiar with managing setuid root programs and the

    security issues they present, we highly recommend that you not

    consider using suEXEC.</p>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="before" name="before">Before we begin.</a></h3>

    <p align="LEFT">Before jumping head-first into this document,

    you should be aware of the assumptions made on the part of the

    Apache Group and this document.</p>

    <p align="LEFT">First, it is assumed that you are using a UNIX

    derivate operating system that is capable of

    <strong>setuid</strong> and <strong>setgid</strong> operations.

    All command examples are given in this regard. Other platforms,

    if they are capable of supporting suEXEC, may differ in their

    configuration.</p>

    <p align="LEFT">Second, it is assumed you are familiar with

    some basic concepts of your computer's security and its

    administration. This involves an understanding of

    <strong>setuid/setgid</strong> operations and the various

    effects they may have on your system and its level of

    security.</p>

    <p align="LEFT">Third, it is assumed that you are using an

    <strong>unmodified</strong> version of suEXEC code. All code

    for suEXEC has been carefully scrutinized and tested by the

    developers as well as numerous beta testers. Every precaution

    has been taken to ensure a simple yet solidly safe base of

    code. Altering this code can cause unexpected problems and new

    security risks. It is <strong>highly</strong> recommended you

    not alter the suEXEC code unless you are well versed in the

    particulars of security programming and are willing to share

    your work with the Apache Group for consideration.</p>

    <p align="LEFT">Fourth, and last, it has been the decision of

    the Apache Group to <strong>NOT</strong> make suEXEC part of

    the default installation of Apache. To this end, suEXEC

    configuration requires of the administrator careful attention

    to details. After due consideration has been given to the

    various settings for suEXEC, the administrator may install

    suEXEC through normal installation methods. The values for

    these settings need to be carefully determined and specified by

    the administrator to properly maintain system security during

    the use of suEXEC functionality. It is through this detailed

    process that the Apache Group hopes to limit suEXEC

    installation only to those who are careful and determined

    enough to use it.</p>

    <p align="LEFT">Still with us? Yes? Good. Let's move on!</p>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="model" name="model">suEXEC Security Model</a></h3>

    <p align="LEFT">Before we begin configuring and installing

    suEXEC, we will first discuss the security model you are about

    to implement. By doing so, you may better understand what

    exactly is going on inside suEXEC and what precautions are

    taken to ensure your system's security.</p>

    <p align="LEFT"><strong>suEXEC</strong> is based on a setuid

    "wrapper" program that is called by the main Apache web server.

    This wrapper is called when an HTTP request is made for a CGI

    or SSI program that the administrator has designated to run as

    a userid other than that of the main server. When such a

    request is made, Apache provides the suEXEC wrapper with the

    program's name and the user and group IDs under which the

    program is to execute.</p>

    <p align="LEFT">The wrapper then employs the following process

    to determine success or failure -- if any one of these

    conditions fail, the program logs the failure and exits with an

    error, otherwise it will continue:</p>

    <ol>

      <li>

        <strong>Was the wrapper called with the proper number of

        arguments?</strong> 

        <blockquote>

          The wrapper will only execute if it is given the proper

          number of arguments. The proper argument format is known

          to the Apache web server. If the wrapper is not receiving

          the proper number of arguments, it is either being

          hacked, or there is something wrong with the suEXEC

          portion of your Apache binary.

        </blockquote>

      </li>

      <li>

        <strong>Is the user executing this wrapper a valid user of

        this system?</strong> 

        <blockquote>

          This is to ensure that the user executing the wrapper is

          truly a user of the system.

        </blockquote>

      </li>

      <li>

        <strong>Is this valid user allowed to run the

        wrapper?</strong> 

        <blockquote>

          Is this user the user allowed to run this wrapper? Only

          one user (the Apache user) is allowed to execute this

          program.

        </blockquote>

      </li>

      <li>

        <strong>Does the target program have an unsafe hierarchical

        reference?</strong> 

        <blockquote>

          Does the target program contain a leading '/' or have a

          '..' backreference? These are not allowed; the target

          program must reside within the Apache webspace.

        </blockquote>

      </li>

      <li>

        <strong>Is the target user name valid?</strong> 

        <blockquote>

          Does the target user exist?

        </blockquote>

      </li>

      <li>

        <strong>Is the target group name valid?</strong> 

        <blockquote>

          Does the target group exist?

        </blockquote>

      </li>

      <li>

        <strong>Is the target user <em>NOT</em> superuser?</strong>

        <blockquote>

          Presently, suEXEC does not allow 'root' to execute

          CGI/SSI programs.

        </blockquote>

      </li>

      <li>

        <strong>Is the target userid <em>ABOVE</em> the minimum ID

        number?</strong> 

        <blockquote>

          The minimum user ID number is specified during

          configuration. This allows you to set the lowest possible

          userid that will be allowed to execute CGI/SSI programs.

          This is useful to block out "system" accounts.

        </blockquote>

      </li>

      <li>

        <strong>Is the target group <em>NOT</em> the superuser

        group?</strong> 

        <blockquote>

          Presently, suEXEC does not allow the 'root' group to

          execute CGI/SSI programs.

        </blockquote>

      </li>

      <li>

        <strong>Is the target groupid <em>ABOVE</em> the minimum ID

        number?</strong> 

        <blockquote>

          The minimum group ID number is specified during

          configuration. This allows you to set the lowest possible

          groupid that will be allowed to execute CGI/SSI programs.

          This is useful to block out "system" groups.

        </blockquote>

      </li>

      <li>

        <strong>Can the wrapper successfully become the target user

        and group?</strong> 

        <blockquote>

          Here is where the program becomes the target user and

          group via setuid and setgid calls. The group access list

          is also initialized with all of the groups of which the

          user is a member.

        </blockquote>

      </li>

      <li>

        <strong>Does the directory in which the program resides

        exist?</strong> 

        <blockquote>

          If it doesn't exist, it can't very well contain files.

        </blockquote>

      </li>

      <li>

        <strong>Is the directory within the Apache

        webspace?</strong> 

        <blockquote>

          If the request is for a regular portion of the server, is

          the requested directory within the server's document

          root? If the request is for a UserDir, is the requested

          directory within the user's document root?

        </blockquote>

      </li>

      <li>

        <strong>Is the directory <em>NOT</em> writable by anyone

        else?</strong> 

        <blockquote>

          We don't want to open up the directory to others; only

          the owner user may be able to alter this directories

          contents.

        </blockquote>

      </li>

      <li>

        <strong>Does the target program exist?</strong> 

        <blockquote>

          If it doesn't exists, it can't very well be executed.

        </blockquote>

      </li>

      <li>

        <strong>Is the target program <em>NOT</em> writable by

        anyone else?</strong> 

        <blockquote>

          We don't want to give anyone other than the owner the

          ability to change the program.

        </blockquote>

      </li>

      <li>

        <strong>Is the target program <em>NOT</em> setuid or

        setgid?</strong> 

        <blockquote>

          We do not want to execute programs that will then change

          our UID/GID again.

        </blockquote>

      </li>

      <li>

        <strong>Is the target user/group the same as the program's

        user/group?</strong> 

        <blockquote>

          Is the user the owner of the file?

        </blockquote>

      </li>

      <li>

        <strong>Can we successfully clean the process environment

        to ensure safe operations?</strong> 

        <blockquote>

          suEXEC cleans the process' environment by establishing a

          safe execution PATH (defined during configuration), as

          well as only passing through those variables whose names

          are listed in the safe environment list (also created

          during configuration).

        </blockquote>

      </li>

      <li>

        <strong>Can we successfully become the target program and

        execute?</strong> 

        <blockquote>

          Here is where suEXEC ends and the target program begins.

        </blockquote>

      </li>

    </ol>

    <br />

     <br />

    <p align="LEFT">This is the standard operation of the the

    suEXEC wrapper's security model. It is somewhat stringent and

    can impose new limitations and guidelines for CGI/SSI design,

    but it was developed carefully step-by-step with security in

    mind.</p>

    <p align="LEFT">For more information as to how this security

    model can limit your possibilities in regards to server

    configuration, as well as what security risks can be avoided

    with a proper suEXEC setup, see the <a

    href="#jabberwock">"Beware the Jabberwock"</a> section of this

    document.</p>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="install" name="install">Configuring &amp; Installing

    suEXEC</a></h3>

    <p align="LEFT">Here's where we begin the fun. If you use

    Apache 1.2 or prefer to configure Apache 1.3 with the

    "<code>src/Configure</code>" script you have to edit the suEXEC

    header file and install the binary in its proper location

    manually. The following sections describe the configuration and

    installation for Apache 1.3 with the AutoConf-style interface

    (APACI).</p>

    <p align="LEFT"><strong>APACI's suEXEC configuration

    options</strong><br />

    </p>

    <dl>

      <dt><code>--enable-suexec</code></dt>

      <dd>This option enables the suEXEC feature which is never

      installed or activated by default. At least one

      --with-suexec-xxxxx option has to be provided together with the

      --enable-suexec option to let APACI accept your request for

      using the suEXEC feature.</dd>

      <dt><code>--with-suexec-caller=<em>UID</em></code></dt>

      <dd>The <a href="mod/mpm_common.html#user">username</a> under which

      Apache normally runs. This is the only user allowed to

      execute this program.</dd>

      <dt><code>--with-suexec-docroot=<em>DIR</em></code></dt>

      <dd>Define as the DocumentRoot set for Apache. This will be

      the only hierarchy (aside from UserDirs) that can be used for

      suEXEC behavior. The default directory is the --datadir value

      with the suffix "/htdocs", <em>e.g.</em> if you configure

      with "<code>--datadir=/home/apache</code>" the directory

      "/home/apache/htdocs" is used as document root for the suEXEC

      wrapper.</dd>

      <dt><code>--with-suexec-logfile=<em>FILE</em></code></dt>

      <dd>This defines the filename to which all suEXEC

      transactions and errors are logged (useful for auditing and

      debugging purposes). By default the logfile is named

      "suexec_log" and located in your standard logfile directory

      (--logfiledir).</dd>

      <dt><code>--with-suexec-userdir=<em>DIR</em></code></dt>

      <dd>Define to be the subdirectory under users' home

      directories where suEXEC access should be allowed. All

      executables under this directory will be executable by suEXEC

      as the user so they should be "safe" programs. If you are

      using a "simple" UserDir directive (ie. one without a "*" in

      it) this should be set to the same value. suEXEC will not

      work properly in cases where the UserDir directive points to

      a location that is not the same as the user's home directory

      as referenced in the passwd file. Default value is

      "public_html".<br />

       If you have virtual hosts with a different UserDir for each,

      you will need to define them to all reside in one parent

      directory; then name that parent directory here. <strong>If

      this is not defined properly, "~userdir" cgi requests will

      not work!</strong></dd>

      <dt><code>--with-suexec-uidmin=<em>UID</em></code></dt>

      <dd>Define this as the lowest UID allowed to be a target user

      for suEXEC. For most systems, 500 or 100 is common. Default

      value is 100.</dd>

      <dt><code>--with-suexec-gidmin=<em>GID</em></code></dt>

      <dd>Define this as the lowest GID allowed to be a target

      group for suEXEC. For most systems, 100 is common and

      therefore used as default value.</dd>

      <dt><code>--with-suexec-safepath=<em>PATH</em></code></dt>

      <dd>Define a safe PATH environment to pass to CGI

      executables. Default value is

      "/usr/local/bin:/usr/bin:/bin".</dd>

    </dl>

    <br />

     <br />

    <p align="LEFT"><strong>Checking your suEXEC

    setup</strong><br />

     Before you compile and install the suEXEC wrapper you can

    check the configuration with the --layout option.<br />

     Example output:</p>

<pre>

    suEXEC setup:

            suexec binary: /usr/local/apache/sbin/suexec

            document root: /usr/local/apache/share/htdocs

           userdir suffix: public_html

                  logfile: /usr/local/apache/var/log/suexec_log

                safe path: /usr/local/bin:/usr/bin:/bin

                caller ID: www

          minimum user ID: 100

         minimum group ID: 100

</pre>

    <br />

     <br />

    <p align="LEFT"><strong>Compiling and installing the suEXEC

    wrapper</strong><br />

     If you have enabled the suEXEC feature with the

    --enable-suexec option the suexec binary (together with Apache

    itself) is automatically built if you execute the command

    "make".<br />

     After all components have been built you can execute the

    command "make install" to install them. The binary image

    "suexec" is installed in the directory defined by the --sbindir

    option. Default location is

    "/usr/local/apache/sbin/suexec".<br />

     Please note that you need <strong><em>root

    privileges</em></strong> for the installation step. In order

    for the wrapper to set the user ID, it must be installed as

    owner <code><em>root</em></code> and must have the setuserid

    execution bit set for file modes.</p>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="enable" name="enable">Enabling &amp; Disabling

    suEXEC</a></h3>

    <p align="LEFT">Upon startup of Apache, it looks for the file

    "suexec" in the "sbin" directory (default is

    "/usr/local/apache/sbin/suexec"). If Apache finds a properly

    configured suEXEC wrapper, it will print the following message

    to the error log:</p>

<pre>

    [notice] suEXEC mechanism enabled (wrapper: <em>/path/to/suexec</em>)

</pre>

    If you don't see this message at server startup, the server is

    most likely not finding the wrapper program where it expects

    it, or the executable is not installed <em>setuid root</em>.

    <br />

     If you want to enable the suEXEC mechanism for the first time

    and an Apache server is already running you must kill and

    restart Apache. Restarting it with a simple HUP or USR1 signal

    will not be enough. <br />

     If you want to disable suEXEC you should kill and restart

    Apache after you have removed the "suexec" file. <br />

     <br />

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="usage" name="usage">Using suEXEC</a></h3>

    <p align="LEFT"><strong>Virtual Hosts:</strong><br />

     One way to use the suEXEC wrapper is through the <a

    href="mod/mpm_common.html#user">User</a> and <a

    href="mod/mpm_common.html#group">Group</a> directives in <a

    href="mod/core.html#virtualhost">VirtualHost</a> definitions.

    By setting these directives to values different from the main

    server user ID, all requests for CGI resources will be executed

    as the <em>User</em> and <em>Group</em> defined for that

    <code>&lt;VirtualHost&gt;</code>. If only one or neither of

    these directives are specified for a

    <code>&lt;VirtualHost&gt;</code> then the main server userid is

    assumed.</p>

    <p><strong>User directories:</strong><br />

     The suEXEC wrapper can also be used to execute CGI programs as

    the user to which the request is being directed. This is

    accomplished by using the "<strong><code>~</code></strong>"

    character prefixing the user ID for whom execution is desired.

    The only requirement needed for this feature to work is for CGI

    execution to be enabled for the user and that the script must

    meet the scrutiny of the <a href="#model">security checks</a>

    above.</p>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="debug" name="debug">Debugging suEXEC</a></h3>

    <p align="LEFT">The suEXEC wrapper will write log information

    to the file defined with the --with-suexec-logfile option as

    indicated above. If you feel you have configured and installed

    the wrapper properly, have a look at this log and the error_log

    for the server to see where you may have gone astray.</p>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <h3><a id="jabberwock" name="jabberwock">Beware the Jabberwock:

    Warnings &amp; Examples</a></h3>

    <p align="LEFT"><strong>NOTE!</strong> This section may not be

    complete. For the latest revision of this section of the

    documentation, see the Apache Group's <a

    href="http://www.apache.org/docs/suexec.html">Online

    Documentation</a> version.</p>

    <p align="LEFT">There are a few points of interest regarding

    the wrapper that can cause limitations on server setup. Please

    review these before submitting any "bugs" regarding suEXEC.</p>

    <ul>

      <li><strong>suEXEC Points Of Interest</strong></li>

      <li>

        Hierarchy limitations 

        <blockquote>

          For security and efficiency reasons, all suexec requests

          must remain within either a top-level document root for

          virtual host requests, or one top-level personal document

          root for userdir requests. For example, if you have four

          VirtualHosts configured, you would need to structure all

          of your VHosts' document roots off of one main Apache

          document hierarchy to take advantage of suEXEC for

          VirtualHosts. (Example forthcoming.)

        </blockquote>

      </li>

      <li>

        suEXEC's PATH environment variable 

        <blockquote>

          This can be a dangerous thing to change. Make certain

          every path you include in this define is a

          <strong>trusted</strong> directory. You don't want to

          open people up to having someone from across the world

          running a trojan horse on them.

        </blockquote>

      </li>

      <li>

        Altering the suEXEC code 

        <blockquote>

          Again, this can cause <strong>Big Trouble</strong> if you

          try this without knowing what you are doing. Stay away

          from it if at all possible.

        </blockquote>

      </li>

    </ul>

    <p align="CENTER"><strong><a href="suexec.html">BACK TO

    CONTENTS</a></strong></p>

    <!--#include virtual="footer.html" -->

  </body>

</html>